The present invention relates to a resin pipe (including hose) which is formed of a resin material such as rubber, synthetic rubber, synthetic resin, or the like, and in which a number of reinforcing threads are buried in the pipe wall. More particularly, the present invention relates to a resin pipe in which a pipe wall is formed so as to have two or more layers and a number of reinforcing threads are buried between the layers.
Conventionally, a synthetic resin pipe in which a number of reinforcing threads are buried in the pipe wall, is generally known. Further, a pipe in which such reinforcing threads are buried in the pipe wall along the length thereof, and a pipe in which such reinforcing threads are buried so as to cross each other along the obliquely circumferential directions of the pipe wall, are generally known.
In those conventional synthetic resin pipes, regardless of the method of thread arrangement employed in the respective synthetic resin pipes, one kind of reinforcing threads, that is, reinforcing threads of one kind of color, are buried in one pipe. This is because reinforcing threads are buried only for the purpose of reinforcing a pipe wall. Therefore, only one kind of reinforcing threads are sufficient to attain such a purpose of reinforcement. In this point, there is no special problem.
In such a reinforcing-thread-buried resin pipe, however, in order to make indication as to the machine and factory by which and in which the pipe is produced respectively, it is necessary to give an indication by making printing on the pipe when the pipe is produced.
As means for performing such printing, it is possible to consider two kinds of means, that is, means using ink and means for giving baking indication. In the case of using ink, there are various problems that the ink spread property is poor because the object to be printed is resin, the ink may become dirty if the other thing touches the ink before it has been dried completely, the ink is apt to be erased by being touched by other things even after dried, and so on, while, in the case of baking printing, it is difficult to give clear indication, the surface of the pipe is apt to be injured, it is difficult to see the indication, and so on.
Further, in either case of foregoing conventional printing means, there are various problems that printing cannot be carried out surely because the printing surface is curved and this curved surface varies in accordance with the diameter of the pipe. Also, additional labor for printing is required in addition to the pipe producing process. The indication cannot be recognized in a portion between the printed portions even if printing is performed at predetermined intervals. The reduction of printed intervals brings about an increase of the cost. Positioning of printing is difficult and displacement in timing is apt to occur in the case of a pipe having a corrugate outer circumferential surface because the printing position is limited.